In my co-pending patent application (USSN 925,296, filed Oct. 31, 1986) an improved silver recovery system is disclosed for the recovery of silver from waste, acidic photographic processing fluid. The fluid is passed through finely divided iron contained a minor amount of a metal salt of copper or cadmium. Substantial improvement in the amount of recoverable silver and in the flow-through characteristics is achieved. However, the useful life of the device which employs this recovery process is not as great as would be predicted from a knowledge of the amount of finely divided iron that is present therein. If all iron present were to be exchanged for silver in the processed fluids, the useable life of this device could be greatly enhanced. Such an improvement would enable the system to be more cost efficient since the user need not change the unit so often.
There is a need to further improve the process of the aforementioned co-pending application so that more of the silver present in a waste, acidic photographic processing fluid can be recovered based on the amount of iron present.